Construct Validity Of The Myotest® In Measuring Force And Power Production

The purpose of this investigation was to determine the construct validity of the Myotest instrument by comparing it the “gold standard” force plate and linear transducer data when measuring force and power production in the bench press/bench throw and squat/squat jump in men and women. In this study 54 men and 43 women (age range18 to 30 yrs) gave informed consent to participate in the investigation. In order to produce a normal distribution a wide range of strength fitness capabilities were represented by the subjects who participated in the study (1 RM strength ranges when using the Smith machine: bench press: women-18-80 kg, men- 39-171 kg; Squat women 30-115 kg, men-75-221 kg. In addition, to the Myotest device placed on the bar, two directly interfaced computerized systems (Ballistic Measurement System [BMS] Innervations Inc, Fitness Technology force plate,. Australia), were used to validate and assess the experimental variables during both 1 repetition maximum (RM) maximal strength test and during power testing using the BMS Smith machine set up. Subjects performed a 1 RM test for both the squat and bench press exercises in which maximal force was measured during the 1 RM repetition. Power testing consisted of subjects performing the jump squat and the bench throw on the BMS at 30% of their 1RM. Regression analysis was used to determine pair wise relationships between the Myotest instrument and the direct online measurement systems. Significance in this study was set at P≤0.05. All assumptions for linear statistics were met and statistical power was ≥ 0.89. Similar relationships were observed for men and women. The reliability of the measures demonstrated intra-class correlation coefficients of R ≥ 0.96. The overall simple regression analyses for the Myotest to the direct measurement systems demonstrated high significant correlations with the following results presented as R2 to represent the amount of shared variance between the measures: bench throw force, R2= 0.92, bench throw power R2= 0.93, squat jump force R2= 0.97, squat jump power R2= 0.82. The Myotest instrument demonstrated a high reliability in testing strength and power. In addition, the Myotest instrument demonstrated a high set of construct validity scores in measuring strength and power in men and women of various strength fitness capabilities. The Myotest instrument represents an appropriate instrument and a valid method for measuring force and power in commonly used strength and power exercise movements.